Chaotic Time-Delay Signature Suppression and Entropy Growth Enhancement Using Frequency-Band Extractor

TL;DR

This paper presents a method using frequency-band extraction to significantly suppress time-delay signatures and enhance entropy growth in chaotic laser signals, improving randomness for secure communications.

Contribution

It introduces a novel frequency-band extraction technique that effectively suppresses TDS and boosts entropy in chaotic lasers, supported by experimental and theoretical validation.

Findings

TDS suppressed up to 96% at optimal bandwidth

Entropy growth exceeds noise threshold, indicating increased randomness

Skewness of laser intensity distribution improved to 0.001

Abstract

By frequency-band extracting, we experimentally and theoretically investigate time-delay signature (TDS) suppression and entropy growth enhancement of a chaotic optical-feedback semiconductor laser under different injection currents and feedback strengths. The TDS and entropy growth are quantified by the peak value of autocorrelation function and the difference of permutation entropy at the feedback delay time. At the optimal extracting bandwidth, the measured TDS is suppressed up to 96% compared to the original chaos, and the entropy growth is higher than the noise-dominated threshold indicating that the dynamical process is noisy. The effects of extracting bandwidth and radio frequencies on the TDS and entropy growth are also clarified experimentally and theoretically. The experimental results are in good agreements with the theoretical results. The skewness of the laser intensity distribution is effectively improved to 0.001 with the optimal extracting bandwidth. This technique provides a promising tool to extract randomness and prepare desired entropy sources for chaotic secure communication and random number generation.